Sample introduction systems hyphenated techniques

Because ICP-MS with different instrumentations and sample introduction systems (besides solution nebulization, also laser ablation or hyphenated methods, such as HPLC, CE, SPME) is today the most frequently used analytical technique for precise and accurate isotope ratio measurements, the following section will mainly focus on this form of mass spectrometry with an inductively coupled plasma source. 

An examination of the publication trends concerning the use of ICP-MS in food-related areas (Fig. 8.6) shows that after less than one decade from its first application in this field, the number of published works increased by a factor of 10. In recent years, about 50-70 papers on food-related topics have appeared annually and nearly half of them concern speciation topics. ICP-MS represents today an essential tool for inorganic and bioinorganic research on foods and its versatility, that is, the ease of coupling with different sample introduction systems, as well as the hyphenation with devices for species separation, is undoubtedly a key point of its success. Moreover, the progress in instrumentation has overcome most of the past limitations of the technique and with the availability of MC-, CC-, and DRC-ICP-MS instruments a growing number of applications in any area of food and nutrition research are expected. 

A current trend is the coupling of another technique with AES, such as liquid chromatography, ion chromatography, or flow injection analysis, to enhance the capability of the plasma, particularly in the field of speciation (the so-called hyphenated techniques). This coupling can be considered as a highly sophisticated sample introduction system. In... 

ICP is seeing more use as a sample introduction system for various hyphenated techniques. New to the pharmaceutical industry is the use of inductively coupled plasma-mass spectrometry (ICP-MS). ICP-MS offers excellent versatihty and sensitivity to the analyst, and greatly complements any pharmaceutical... 

Various efficient devices have been utilized for sample introduction into an inductive plasma source, for example the application of several nebulizers, hyphenated techniques, hydride generation, laser ablation and electrothermal vaporization. The role of the solution introduction system in an inductively coupled plasma source is to convert the liquid sample into a suitable form (e.g.,... 

Conventional packed column injection ports are used for the sample introduction on packed and megabore columns. In case of capillary columns, unless a special injection technique is used, the low maximum allowable sample volume which may be introduced on the column negatively affects the experimental detection limits as only a tiny fraction of the derivatized extract is finally processed in the hyphenated system. Online preconcentration and injection of derivatized organolead species can solve that problem. It consists of three consecutive processes taking place in the injection hner sample injection, solvent venting and release of the analytes on to the column. Up to 25 fil can be processed at a time and larger amounts can be handled by successive injections of 20 to 25 /a1 volumes at 1 min intervals to remove the solvent. 

Chapters on sample introduction and hyphenated sample treatment and ICP systems have also been further updated since the last edition. No doubt that chromatographic, electrophoresis, flow injection and field flow fraction separations have extended ICP-MS (and AES) measurements as the mainstay of elanental specia-tion measurements in biological and environmental fields. Without the combination of these separation techniques and ICP measurements, elemental speciation applications would be severely hampered... if not impossible (Chapter 18). The ability to measure P and S with high sensitivity has opened up new opportunities in proteomics, for example. Species-specific and unspecific isotopic dilution (ID-MS) has been critical in quantifying speciation analysis and revealing recovery errors (Chapter 13). Species-specific techniques have been applied to identify species transformations, resulting in the development of multi-species methods whereas, hyphenated species-unspecific ICP-ID-MS determinations of heteroatoms such as sulfur have become a common quantification technique in proteomics. 

Section 6.4 deals with other EI-MS analyses of samples, i.e. analyses using direct introduction methods (reservoir or reference inlet system and direct insertion probe). Applications of hyphenated electron impact mass-spectrometric techniques for poly-mer/additive analysis are described elsewhere GC-MS (Section 7.3.1.2), LC-PB-MS (Section 7.3.3.2), SFC-MS (Section 13.2.2) and TLC-MS (Section 7.3.5.4). 

---